484 



THE POPULAR SCIENCE MONTHLY. 



in this country and Europe, and in both rapidly going into use, we 

 have a machine that is a very satisfactory solution of the problems 

 involved in the construction of this class of motors. In the matter of 

 fuel it is nearly, if not quite, as economical as a steam-engine of cor- 

 responding power, and is, therefore, in actual use much more so, both 



because no engineer is required to run it and the expense of keeping 

 up steam, whether running or not, is avoided. The combustible charge 

 introduced into the cylinder is composed of gas and air in such pro- 

 portions that rapid combustion instead of an explosion takes place, 

 and, to obtain sufficient pressure from its expansion, it is compressed 

 to one third its original volume before being ignited. 



